RNA Mediated Interference RNAi - Silencing of homologous gene expression triggered by double stranded RNA (dsRNA) is called RNA mediated interference or RNA interference (RNAi). Introduction of long double stranded RNA into the cells of plants, invertebrates as well as mammals leads to a sequence specific degradation of the homologous gene transcripts.

The long dsRNA molecules are cleaved by an RNase III enzyme called Dicer; this generates small 21-23 nucleotide long dsRNA molecules called small interfering RNAs (siRNAs).

The siRNA molecules bind to a protein complex called RNA-induced silencing complex; this complex contains a helicase activity that unwinds the two strands of RNA molecules.